Obesity is primarily a consequence of detrimental nutritional and physical habits against an unfavorable genetic background. It is a major risk factor for the development of common medical conditions such as the metabolic syndrome, type 2 diabetes mellitus and cardiovascular disease. As a metabolically active organ, the human intestine contains a dense and diverse community of micro-organisms, dominated by over a thousand different bacterial species. There is growing evidence for the role of intestinal microbiota in host metabolism.
The phyla that account for the vast majority of intestinal microbiota include the Gram-negative Bacteroidetes, Proteobacteria and Verrucomicrobia, as well as the Gram-positive Firmicutes and Actinobacteria. It was previously shown that the gut microbiota contributes to the development of diet-induced obesity in mice. The colonic microbiota in obese mice appeared to be characterized by a lower microbial diversity and an enrichment in carbohydrate and lipid-utilizers. Putatively, the short chain fatty acids acetate, propionate and butyrate produced by specific gut bacteria could serve as a signal that directly influences host hepatic and peripheral insulin sensitivity. On the other hand, recent research showed that lower gut microbial diversity in mice was associated with endotoxemia-induced chronic inflammation and subsequent development of insulin resistance.
In humans, altered colonic microbiota have been correlated to obesity, but consensus regarding specific bacterial groups of species and evidence for a causative role is lacking. As metabolically healthy and unhealthy obese phenotypes exist based on the absence or presence of insulin resistance, published reports on associations between intestinal microbiota composition and human obesity seem to be compromised by heterogeneity in the obese phenotype, various confounding factors e.g., diet, medication use) and developing methods to analyze the intestinal microbiota. This is particularly true for the small intestinal microbiota that is relatively inaccessible but is exposed to a large surface. It has been found that the microbial diversity of the small intestine is smaller than that of the colon and is notably enriched in bacteria belonging to the Lactobacillales and Veillonella spp. (Booijnk et al., 2010, Env. Microbiol. 12:3213-27). Thus, there is a need in the art to find further medicaments suitable to treat and/or prevent insulin resistance and/or type 2 diabetes mellitus, preferably medicaments that can be easily incorporated in the patient's lifestyle, for example, in the form of food compositions for daily consumption.